On Tue, 13 Jan 98 15:01:47 -0800 
 "Chris G. Demetriou" <cgd@pa.dec.com> wrote:

 > This is a reasonable way to tell, yes.  "no need for flags, then."  8-)
 > 
 > 
 > >  - 32-bit dev_t split up as {
 > > 	12 bits major
 > > 	20 bits minor {
 > > 	   10 bits "unit"
 > > 	   10 bits "subunit"
 > > 	}
 > >    }
 > >    (interpretation of minor is left to the device itself; disks and
 > >    tapes use the subunit while ttys are generally just sequential);
 > >    ls -l shows <major,unit,subunit> (even on ttys).
 > 
 > What is the definition of 'unit'?  For example, take SCSI.  Does
 > device,LUN -> unit and partition number -> subunit, or does device ->
 > unit and LUN fit into subunit (with other information, e.g. partition
 > number)?  Looking at the list Paul Vixie posted, it looks like the
 > former.

Um ... if you're assigning numbers the way our (Torek's :-) autoconfiguration
does, unit doesn't necessarily map to device,lun ... I would take this
as "unit as far as autoconfiguration is concerned" in all cases.

 > How about multi-port TTY devices (e.g. cyclom boards, etc.?)  In that
 > case, does 'unit' correspond to driver unit, and 'subunit' correspond
 > to the individual ttys, or do the ttys all get their own individual
 > 'unit' numbers?  (I can see logic for either, though probably more
 > justification for the former.  Paul didn't provide much tty
 > information.)

..subunit might also correspond to "mode" ... i.e. "dialout" devices, etc.

Jason R. Thorpe                                       thorpej@nas.nasa.gov
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